Hybrid coatings systems are a route to achieving materials having unique and superior properties that cannot be achieved using only a single component of the hybrid. The sol-gel technique, one of the easy and cost-effective methods to make hybrid coatings, is unique since chemical linkages between the soft organic and the hard inorganic components are established. In this way, one can combine the properties of an organic component such as mechanical toughness and flexibility with the hardness and thermal stability of the inorganic component into a single system. See, e.g. Y. J. Du, M. Damron, G. Tang, H. Zheng, C. J. Chu, J. H. Osborne, Prog. Org, Coat. 41 (2001) 226-232; D. K. Chattopadhyay, K. V. S. N. Raju, Prog. Polym. Sci. 32 (2007) 352-418, herein incorporated by reference in its entirety. In the case of silane based sol-gel systems, the silicon-oxygen bonds of these types of polymers provides the hybrid with a variety of attractive properties. Additionally, due to the hybrid character, sol-gel coatings based on polyurethanes (PUs) or epoxy-amine coatings possess high optical transparency, superior weathering and corrosion resistance, excellent abrasion and impact resistance as well as better adhesive properties than the base material. Depending on the desired field of application, coatings with different thermo-mechanical properties can be obtained due to the versatility in the formulation variables of the organic components, inorganic components and sol-gel processing parameters. The inorganic phase is obtained from the hydrolysis and condensation reactions in the sol-gel process of metal alkoxides of the type RM(OCnH2n+1)3, where R is a suitable organic group and M is Si, Ti, Al, Sn or Zr. The appropriate choice of R enables one to synthesize hybrids with a wide variety of properties. Organosilanes such as 3-aminopropyl trimethoxysilane (APTMS) and N-(2-aminoethyl) 3-aminopropyl trimethoxysilane (AEAPTMS) are widely used precursors of silica in the sol-gel process to obtain ceramer coatings. These can be further modified with a tetrafunctional alkoxysilane such as tetraethylorthosilicate (TEOS).
Alkoxy silane functional polyureas have been synthesized from the reaction of a the isocyanurate trimer of hexamethylene diisocyanate and 3-aminopropyl trimethoxy silane and these have been used to make a moisture curing hybrid coating. See H. Ni, D. J. Aaserudb, W. J. Simonsick Jr., M. D. Soucek, Polymer 41 (2000)57-71; and H. Ni, A. D. Skaja, R. A. Sailer, M. D. Soucek, Macromol. Chem. Phys. 201 (2000)722-732, both of which are herein incorporated by reference in their entirety. Coatings were also prepared incorporating TEOS in addition to the silane modified polyurea. See H. Ni, A. D. Skaja, M. D. Soucek, Prog. Org. Coat. 40 (2000)175-184; and H. Ni, W. 3. Simonsick, A. D. Skaja, J. P. Williams, M. D. Soucek, Prog. Org. Coat. 38 (2000)97-110, both of which are herein incorporated by reference in their entirety.
A monofunctionalized isocyanurate was prepared from the reaction of one mole of the isocyanurate trimer of hexamethylene diisocyanate and one mole of 3-aminopropyl trimethoxysilane. See H. Ni, A. H. Johnson, M. D. Soucek, J. T. Grant, A. J. Vreugdenhil, Macromol. Mater. Eng. 287 (2002)470-479; and M. D. Soucek, H. Hai, J. Coat. Technol. 74(933) (2002)125-134, both of which are herein incorporated by reference in their entirety. Hybrid coatings were made from a combination of the monofunctionalized resin, a polyester polyol and TEOS.
A shape memory polyurethane system was synthesized by first preparing a diol from the Michael reaction of two moles of hydroxylethyl acrylate with 3-aminopropyl trimethoxy silane. The diol was then incorporated into a linear polyurethane and then crosslinked by the hydrolysis-condensation of the silane functional groups. See J. Xu, W. Shi, W. Pang, Polymer 47 (2006)457-465, herein incorporated by reference in its entirety.
A hybrid epoxy silica hybrid material was synthesized by mixing glycidoxypropyl trimethoxy silane, a bisphenol-A diglycidyl ether epoxy resin and an amine crosslinker. See S. R. Davis, A. R. Brough, A. Atkinson, J. Non-Crystalline Solids 315 (2003)197-205, herein incorporated by reference in its entirety.
An alkoxysilane functional epoxy resin was prepared by reacting the hydroxyl groups in a bisphenol-A diglycidyl ether epoxy resin with isocyanatopropyl triethoxysilane. See R. C. Chang, C. L. Chiang, Y. C. Chiu, J. Appl. Polym. Sci. 106 (2007)3290-3297, herein incorporated by reference in its entirety. An alkoxysilane functional isocyanurate resin was also prepared from the reaction of triglycidyl isocyanurate with aminopropyl triethoxysilane. The two silane modified resins were then combined along with a polyoxypropylene diamine crosslinker to faint the hybrid sol-gel network.
Glycidyl carbamate (GC) functional oligomers can be synthesized by the reaction of the NCO groups in polyfunctional isocyanates with glycidol. See Chen et al., J. Applied Polymer Science, 51, 1199 (1994); and J. Applied Polymer Science, 52, 1137 (1994), both of which are herein incorporated by reference in their entirety. Chen described the preparation of glycidyl-terminated polyurethane resins. Polyamines were used to crosslink the polymers. Blends of the glycidyl-terminated polyurethane resins with conventional epoxy resins were also prepared and crosslinked with polyamines.
Multifunctional GC oligomers may be prepared from isocyanurate trimers of HDI and biuret adducts of HDI, and are called IGC and BGC, respectively. See P. A. Edwards, G. Striemer, D. C. Webster, Prog. Org. Coat. 57 (2006)128-139; and P. A. Edwards, G. Striemer, D. C. Webster, J. Coat. Technol. Research 2(7) (2005)517-527, both of which are herein incorporated by reference in their entirety. These resins are composed of a mixture of the triisocyanate resin plus additional higher molecular weight oligomers. GC functional oligomers will self-crosslink at elevated temperatures to form coatings with good hardness, flexibility, and adhesion. See P. A. Edwards, G. Striemer, D. C. Webster, Prog. Org. Coat. 57 (2006)128-139, herein incorporated by reference in its entirety. GC functional oligomers can also be crosslinked with polyfunctional amines. See P. A. Edwards, G. Striemer, D. C. Webster, J. Coat. Technol. Research 2(7) (2005) 517-527, herein incorporated by reference in its entirety.
Webster, et al., have also disclosed the synthesis of glycidyl carbamate functional resins where part of the glycidol is replaced by alcohols. See U.S. Provisional Application No. 60/976,072, entitled, “Modified Glycidyl Carbamate Resins” filed on Sep. 28, 2007, herein incorporated by reference in its entirety.
Thus, there is an ongoing need in the art for improved silane-functional epoxy urethane compounds and coating compositions containing these compounds, in particular coating compositions that exhibits good adhesion, abrasion resistance, solvent resistance, and thermal stability. This invention answers that need.